Manuel Pellegrini has a first trophy as Manchester City manager, after the Asia Trophy was won by a sweet Edin Dzeko shot, but victory was soured as the Chilean witnessed Matija Nastasic being taken off on a stretcher during the second half.

After a brief pause, the rain that had fallen almost incessantly throughout the week began again in earnest for a contest of which each manager had expressed concerns regarding player safety.

The renewed heavy downpour meant that the final was played in the kind of mudbath reminiscent of 1970s' football in England than the 21st century in Hong Kong.

While the seriousness of Nastasic's injury is yet to emerge, Dzeko, whose semi-final goal against South China proved to be the winner, claimed his second of this tournament, after nine minutes. From outside the area, the forward connected cleanly with the ball to leave Sunderland's goalkeeper, Vito Mannone, no chance.

Alvaro Negredo, making a first start since his £20.6m move, gave an illustration of City's dominance during the opening period, when he too easily created space in the area, though he failed to shoot. In another chance, the Spaniard ran clear but his left-foot effort was high and wild.

On the stroke of half-time, Craig Gardner came close to scoring an own goal when his attempt at a clearing header came back off Mannone's left post – the midfielder himself hurtled head-first into the other upright, though he got to his feet.

Jesus Navas's entrance at half-time for his debut left Stevan Jovetic of City's four summer buys as the last man yet to wear the sky-blue shirt competitively.

On Friday, Paolo Di Canio talked of how the nine new players he has recruited – the Italian has moved out 10 – had instantly integrated into a squad fully on-message. They began the second period as if Di Canio had issued a tart reminder during the break of what he expects, pouring forward to ask questions of City.

But after Adam Johnson gave up possession too easily when dribbling into the area, Sunderland were again pinned back for most of the second half.

On 68 minutes, Dzeko had a chance from the penalty spot to score his second. But the Bosnian spooned a terrible effort over and though he glared at the surface, he had slipped.

Sebastian Larsson's late free-kick forced Costel Pantilimon into a fine save to his right to ensure the deserved result.